Silchar, Jan. 19: The Northeast Frontier (NF) Railway is sending its chief engineer (construction) Arabinda Kumar to Badarpur in Karimganj district of Assam to conduct a ?preliminary probe? into the collapse of a pillar of an under-construction railway bridge over the Barak river on Sunday.

A senior official of the NF Railway (construction) said Kumar is expected to visit the site on Friday to find out why and how the pillar collapsed.

The construction of the bridge is underway as part of the Rs 1,500-crore mega-scheme to convert the 214-km metre gauge line between this town and Lumding junction into a 201-km broad gauge track.

The official said Kumar?s visit would precede a high-level inquiry into the circumstances as well as the causes leading to the collapse of the 22-metre-high pillar of the Rs 29-crore railway bridge, the longest one on the under-construction broad gauge track.

The pillar first tilted towards the right and collapsed headlong on the Barak on Sunday afternoon, throwing five labourers into the river.

Though four among the labourers were rescued by the local people, Mohan Das, a mason, was not that lucky.

A resident of the adjacent Hailakandi district, Das is yet to be traced even as police divers have been scouring for him for the past four days.

The NFR official, while speaking to the media here yesterday but preferring not to be quoted by name, said the railway authorities has been monitoring closely the materials used in the construction of the bridge and there would be no compromise on the quality.

The Tantia Construction Ltd has been executing the construction of the bridge, the foundation of which was laid in 2001 and which was scheduled to be completed by the end of this year. Of the total 10 pillars of the bridge, four have already been raised.

The official said if the need arises, reputed bridge engineers would be brought to the site of the collapse for making an assessment of the quality of work and to suggest its upgradation.

K.K. Gopi, the project engineer of the 409-metre under-construction bridge, told the media that the slushy mud underneath might have led to the tilting of the pillar.

He said the collapsed pillar was to be made 32 metres high, of which 22 metres was raised and its base was stuck under six metres of mud.